Edwaed weston



E. WESTON.

No. 301,027. Patented June 24, 18 84.

N PETERS Pmlo-Limopmplmr. Wnslnnglnm D. Cv

UNITED STATES PATENT OFFICE.

EnwARD wEsToN, E NEWARK, NEW JERsEY, ASSIGNOR To THE UNITED STATES ELECTRIC LIGHTING COMPANY, on NEW YORK, N. Y.

DYNAMO-ELECTRIC MACHINE.

SPECIFICATION forming part of Letters Patent No. 301,027, dated June 24, 1884.

Application filed December .29, 1883. (No model.)

which the devices for utilizing the current areincluded in multiple are or derivation to the r main conductors from the source .of supply. In the system developed and used by me the dynamo-electric machines or generators are constructed in such manner that they develop an electro-motive force that is constant for all variations of resistance in the external circuit within the normal working limits of the machine. The construction of such machines has been described by me in a'former patent, No. 27 8,641, and to such machines of that class as have their field-circuit in derivation to the main or armature circuits my present invention pertains. The development of a constant electro-motive force, however, by such machines presupposes a uniform rate of rotation of the armature; but it may be often necessary to run such machines by an engine of variable speed, in which case the electro-motive force varies. This is primarily due to two causes: first, supposing the speed to increase, to the greater number of lines of force traversed in a given time by the armature-conductors; secondly, to the increased flow of current through the field-magnet coils and the greater magnetic intensity of the field. The converse of this occurs on diminution of the speed.

The object of my invention is to prevent, as far as practicable, these variations by maintaining the magnetism of the field constant; and this I effect by combining with the derived field-circuit an automatic rheostat of any kind, which, by varying theresistance of the field-circuit, maintains through the same a uniform flow of current.

This invention is illustrated in the accom- 5o panying diagram of the system.

A is adynamo-electric machine constructed for developing a constant electro-motive force, as above set forth, and having a derived fieldcircuit, B.

G G are the main conductors from the commutator; D, the cross-circuits, and E the in-' candescent lamps or similar devices included therein.

F is an electromagnet, or its equivalent, such as a helix and core; G, a series of contact-plates; H, a series of resistancecoils connected therewith in the ordinary way.

K is a pivoted contact-arm connected to the core or armature L of the magnet. The coils of the magnet or helix are included in the de- 6 5- rived field-circuit. The rheostat is set or adjusted to include a certain resistance in the field-circuit during the normal running of the machine. If, for any cause, the speed of the machine should increase; the tendency of a stronger current to flow through the field-circuit is checked by the operation of the rheostat, which inserts a greater resistance in the circuit. The converse of this takes place upon a diminution of the speed. In this way the 7 5 magnetism of the field is preserved uniform, so that the ordinary variations of the speed of rotation of the armaturesuch as are likely to occur in practice-produce slight variations in the electro-motive forcedeveloped by the ma- 8o chine.

WVhile the variations in the resistance of the field-circuit might be effected by other means than that shown, I prefer the system illustrated as beingthe most simple and effective. 8 5

I am aware that a variable resistance has been included in the field-circuit of machines, and such I do not claim, broadly; but

WVhat I claim is The combination, with a dynamo-electric 0 machine having a field circuit derived from the main or armature circuit, of a variable resistance and electro-magnet foroperating the same, both included in the field-circuit, as and for the purpose specified. 9 5

In testimony whereof I have hereunto set my hand this 23d day of November, 1883.

EDWVARD WVESTON. 

